1. Field of the Invention
This invention relates generally to face masks, and is more particularly concerned with an improved face mask for a self contained breathing apparatus.
2. Discussion of the Prior Art
A face mask for a self contained breathing apparatus (SCBA) generally includes about six straps fixed to the face mask and to the head harness. The straps, typically, are elastic, and pass through roller buckles to allow easy tightening of the straps. The technique is to tighten each of the six straps to pull the mask's seal tightly against the face to effect a good seal. Since the straps are elastic, however, they tend to pull a person's hair during tightening. Further, the six straps and buckles are arranged so the person must pull on the straps in a direction towards his back to tighten the straps. This is an awkward task, and renders tightening of the mask slow and difficult. It is well known also that rubber tends to deteriorate from exposure to the ambient atmosphere, which may include chorine, ozone and other damaging chemicals. As a result, the straps may break at any time, without prior warning. If even one strap breaks, it will be understood that the seal between the mask and the person's face may be compromised since all six straps are tightened to effect the seal.
Another problem with the prior art face masks is the requirement for three different sizes of mask. Much of the reason for the different sizes is in the nose cup, since adults do not vary widely in the upper portion of the face; thus, the variation is from the bridge of the nose to the chin. Nevertheless, in order to fit everyone, manufacturers have made three different sizes of nose cups to fit the small, medium and large faces. Each of these sizes requires a different mold, which is quite expensive, though about 90% of the sales are of the medium size.
A great number of people have some refractive error in their normal eyesight, requiring correction with glasses. For people using face masks, the use of corrective lenses has been expensive and troublesome. One technique is to have the corrective lenses ground into the face mask itself. This is usually very expensive, and does not allow the sharing of masks. Another technique is to attach spectacles to nibs fixed to the mask, the nibs being adapted to receive the spectacle frames at the usual hinge point for the temple pieces. This arrangement causes difficulty in affixing the spectacles properly, and is time consuming. Another technique is to fix the spectacles to a bracket or the like that is fixed to the face plate. Again, there is some difficulty in obtaining proper alignment.
The seal around the face mask is a source of some problems. For a firefighter or the like who wears a helmet while wearing a face mask, the seal of the face mask tends to interfere with the helmet, rendering the helmet uncomfortable. Also, many people's heads are slightly smaller at the temples, which militates against a secure seal at the temples.
Thus, the prior art has not provided a face mask for a self contained breathing apparatus that is easily adaptable to a variety of different people with different physiognomies.